1. Technical Field
This invention pertains to the manufacture of absorbent products. Such products may be used, for example, in diapers and feminine hygiene products.
2. Description of the Prior Art
A conventional product for use, for example, as a diaper may include a liquid impermeable backsheet, a layer of fluff pulp, an acquisition layer which may be, for example an air laid polypropylene medium, and possibly a spun-bonded polypropylene or nylon layer to be placed next to the skin. Included within the fluff pulp layer may be particles of a super-absorbent material such as, for example, a super-absorbent acrylic-based polymer obtained from Stockhausen Corporation, Greensboro, N.C. These super-absorbent particles absorb water and swell markedly. Upon swelling, the particles tend to interlock with one another, thereby forming a gel. This gel inhibits the passage and absorption of additional liquid.
In order to overcome the gelling problem, it has been proposed to incorporate into the material a laminate containing particles of non-gelling super-absorbent polymers. An example of such a laminate will be found in co-pending U.S. patent application Ser. No. 08/813055 now U.S. Pat. No. 5,792,513, filed Mar. 7, 1997 by Evan E. Koslow et al. for CONTINUOUS SOLID STATE WEB COATING PROCESS. That application is incorporated herein by reference. The disclosure of the referenced application describes the coating of a thin substrate web, such as tissue paper, with an admixture of super-absorbent polymer particles and much smaller particles of a thermoplastic binder. This mixture is applied to the substrate web by the application of pressure and heat sufficient to soften the binder particles. The binder particles are hydrophobic and thereby prevent the water-swollen super-absorbent particles from coalescing into a gel. Also available for such purposes are particles of super-absorbent polymers having cross-linked surfaces which tend to be anti-gel-blocking. A preferred form of the coated web described in the reference application comprises two tissue layers which form a sandwich with the absorbent and binder particles therebetween.
Laminated absorbent pads have been prepared utilizing the customary liquid-impermeable back sheet, but substituting the above-mentioned non-gelling laminate for the fluff pulp layer. An acquisition layer for the laminate comprises an air laid medium having copious large capillaries. Finally, a spun-bonded material may be employed as a skin contact layer. Tests have revealed that such a produce employing a non-gelling laminate will absorb water 30-50% faster than a commercial product employing a fluff pulp core. However, there still remains one problem. While it is advantageous that the super-absorbent particles do not coalesce into a gel, they do create a problem because of their tendency to migrate within the diaper or other product once wetted. In a wet diaper worn by an active toddler, the vastly swollen water-containing particles will not stay in one position but will instead migrate throughout the diaper pad. Accordingly, it is a primary object of the present invention to provide an improved liquid-absorbent pad employing liquid-absorbing laminates wherein migration of the liquid-swollen particles is eliminated or substantially reduced. Other objects, features, and advantages will become apparent from the following description and appended claims.